Find the Local Maximum, and Minimum Value and Saddle Points $f ( x , y ) = x ^ { 2 } - x y + y ^ { 2 } - 9 x + 6 y + 13$

Short Answer

Find the local maximum, and minimum value and saddle points of the function. $f ( x , y ) = x ^ { 2 } - x y + y ^ { 2 } - 9 x + 6 y + 13$